Common installation lock parts are not humanized. During splicing of products, two persons are required to cooperate for operation, which is hard to operate and consumes time and manpower. Since the gravity center at the position of the fixing lock part is hard to locate, arc faces tend to appear after splicing. In addition, common installation lock parts do not have the distance-adjustment function, and consequently the spliced product tends to have gaps. These factors all affect the appearance of the product.